learn about other devices.ppt

7/25/2019 Learn about other Devices.ppt

1/21

1Version 3.1

Module 4Learning About

Other Devices


2/21

2Version 3.1

Cisco Discovery Protocol

A Layer 2 protocol

Obtains information about neighboring Ciscodevices(interfaces, model numbers)

CD !ill discover directly connected Cisco devicesregardless

of !hich Layer " and # protocol suite they run $uns over the %ubnet!or& Access rotocol (%'A)

CDv2 is most recent release

%tarts automatically !hen a device boots up enabled by

default ach Cisco device sendsperiodic advertisementsto multiple

routers (and listens for other messages)

nables net!or& administrators to access a summary of !hat

the configurations loo& li&e on other directly connected routers*


3/21

3Version 3.1

show cdp neighborscommand

Device identifiers - the configured host name of the routerand domain name (if any).

ddress list - t least one !rotocol for "#MP$ u! to one

address for each !rotocol su!!orted.

Port identifier - %thernet &$ %thernet 1$ "erial &$ etc.

Ca!a'ilities list - does the device acts as a 'ridge as ell as

a router

Version - *nformation such as that !rovided 'y the local

command sho version.

Platform - +he device hardare !latform, for eam!le$ Cisco

&&&.

Router#show cdp neighbors (displays CDP updates)


4/21

4Version 3.1

+y!e /ength Value (+/V)+L is simply a piece of information in a CD advertisement

Device *D *dentifies the device name

/ocal interface Contains a list of netor0 addresses of 'oth receivingand transmitting devices

Port *D *dentifies the !ort on hich the CDP !ac0et is sent

Ca!a'ilities Descri'es the devices ca!a'ility 2 i.e. 2 a sitch

Version "oftare release version on hich the device is running

Platform ardare !latform 2 i.e. 2 Cisco 5&&

*P #etor0 Prefi list of netor0 !refies to hich the sending devicecan forard *P !ac0ets

oldtime +he amount of time$ in seconds$ the device directs theneigh'or to hold a CDP advertisement 'efore discardingit


5/21

5Version 3.1

CDP

-f an administrator needs CD information from a Cisco

router that is not directly, then a +elnet session can be

established to connect to another Cisco device that is

connected to the device he needs the information on*

'eeds CD info on this

router, he could telnet to

router above to run sho!

CD neighbors command


6/21

6Version 3.1

CDP Commands


7/217Version 3.1

%na'ling CDP on a 6outer

To enable CDP, use the

cdp run

global confguration

command. CDP is on by deault. Use the no

orm o

this command to disable CDP.

Router(config)#cdp run

+o enable Cisco Discovery rotocol (CD) on an interface,

use the cdp enableinterface configuration command* .se

the noform of this command to disable CD on an interface*

CD is enabled by default on all supported interfaces*

Router(config)#interface serial 0/0

Router(config-if)#cdp enable


8/218Version 3.1

clear cd! counters


9/219

Version 3.1

sho cd!


10/2110

Version 3.1

sho cd! entry


11/2111

Version 3.1

sho cd! interface

"tatus of the

carrier detect

signal

7ee!alive

messages


12/2112

Version 3.1

show cdp neighbors

Router#show cdp neighbors detail !ill

also give the IP addressof the neighboring Ciscodevice

7no this

out!ut8888


13/2113

Version 3.1

9ther cd! commands

show cdp traffic2 sho!s number of pac&ets sent and

received

cdp timer/ specifies ho! often the -O% sends CD

updates

debug cdp/ for debugging all aspects of cdp


14/2114

Version 3.1

+elnet

Part of +CP:*P

suite

6outers have ;

virtual terminal

sessions

Main use is

remote

connection to

netor0

devices


15/21

15Version 3.1

%na'ling CDP on a 6outer

To initiate a Telnet session any o the ollowing

alternatives can be used:

Dener!connect paris

Dener!paris

Dener!""$"0%$"00$"&'

Dener!telnet ""$"0%$"00$"&'

Dener!telnet paris


16/21

16Version 3.1

6eo!ening a sus!ended +elnet session

0ultiple +elnet sessions can be used and suspended by using

the Ctrl-"hift-5, then se1uence*

+hen the session can be resumed by using the nter &ey*

-f the nter &ey is used to resume the session, then Cisco -O%resumes the most recently suspended session*

ou can also use the resumecommand to start up a previous

session, but to do that you must &no! the connection -D*

+o get the connection -D, use the show sessions

command

first, so you can resume the correct session*


17/21

17Version 3.1

6eo!ening a sus!ended +elnet session


18/21

18Version 3.1

+hepingCommand

Ping is a 'asic *nternet !rogram that lets you verify that a!articular *nternet address eists and can acce!t re


19/21

19Version 3.1

>hat Ping can tell you

ing places a uni1ue se1uence number on each pac&et ittransmits, and reports !hich se1uence numbers it receives

bac&* +hus, it can be determine if pac&ets have been dropped,

duplicated, or reordered*

ing places a timestamp in each pac&et, !hich is echoed bac&

and can easily be used to compute ho! long each pac&et

e3change too& / the $ound +rip +ime ($++)*

ing reports other -C0 messages that might other!ise get

buried in the system soft!are* -t reports, for e3ample, if a router

is declaring the target host unreachable*


20/21

20Version 3.1

>hat Ping can not tell you

%ome routers may silently discard undeliverable pac&ets*Others may believe a pac&et has been transmitted successfully

!hen it has not been* (+his is especially common over

thernet, !hich does not provide lin&/layer ac&no!ledgments)

+herefore, ping may not al!ays provide reasons !hy pac&ets

go unans!ered*

ing can not tell you !hy a pac&et !as damaged, delayed, or

duplicated* -t can not tell you !here this happened either,

although you may be able to deduce it*

ing can not give you a blo!/by/blo! description of every host

that handled the pac&et and everything that happened at every

step of the !ay* -t is an unfortunate fact that no soft!are can

reliably provide this information for a +C4- net!or&*


21/21

21

traceroute

traceroute is a utility that records the route through the*nternet 'eteen your com!uter and a s!ecified destination

com!uter

*t also calculates and dis!lays the amount of time each ho!

too0

traceroute tests each ste! (router) along the ay

*f one router in the !ath is unreacha'le$ three asteris0s (???)

ill 'e returned instead of the name of the router

learn about other devices.ppt

Documents